Resistors, capacitors, and inductors are passive elements commonly used in implementing electronic circuits. Resistors absorb electrical energy while capacitors and inductors store electrical energy. Inductors store their energy with current while capacitors store their energy with voltage. Energy storage is found in many electrical systems, including power transformers and antennas.
In addition to energy storage, both inductors and capacitors may shift phase angle of an RF signal. Ability to control phase angles allows for impressing of information onto radio waves. For instance, many RF modulation schemes and antenna designs are based on controlling phase shifts.
Combining energy storage and phase angle control characteristics enable functionality of such devices as filters, resonant tank circuits for oscillators, matching networks, and phase shifters.